The present invention relates to extraction of film image parameters in an image processing apparatus which reads and reproduces film images.
In recent years, various film image reading devices have been proposed which produce color copies of film images in a digital color copying machine.
Now, a description is made of a color copying machine as disclosed in, for example, Japanese Patent Application Unexamined Publication Nos. Hei. 2-189073 and Hei. 2-275938, and a film image reading device to be used in combination with such a color copying machine.
FIG. 5 illustrates one example of the overall configuration of a color copying machine, to which the present invention is applied.
The color copying machine has, as a main part, a base machine 30, which consists of a platen glass 31 on the upper surface of which an original document is to be placed, an image input terminal (IIT) 32, an electrical control system housing unit 33, an image output terminal (IOT) 34, a paper tray 35, and a user interface (U/I) 36. The copying machine may be provided additionally with such optional parts as an editing pad 61, an automatic document feeder (ADF) 62, a sorter 63, and a film projector (F/P) 64.
Electrical hardware is necessary for performing control of the IIT 32, IOT 34, U/I 36, and so forth mentioned above. Such hardware items are divided among a plurality of boards for the individual process units such as the IIT 32, an image processing system (IPS) which image-processes output signals from the IIT 32, the U/I 36 and the F/P 64. These boards are housed in the electrical control system housing unit 33, together with other boards such as a SYS board which controls the above process units, and a machine control board (MCB) which controls the IOT 34, ADF 62, sorter 63, and so on.
The IIT 32, which is comprised of an imaging unit 37, a wire 38 for driving the imaging unit 37, a driving pulley 39, and so forth, reads a color original document for each of the primary colors of light, B (blue), G (green) and R (red), using a CCD line sensor and color filters provided in the imaging unit 37, and converts the data thus read into digital image signals to be output to the IPS.
In the IPS, the B, G, and R signals from the IIT 32 mentioned above are converted into the primary color signals of toners, Y (yellow), C (cyan), M (magenta) and K (black), and, in order to enhance the reproduction performance of colors, chromatic gradation, resolution, and so on, various data processing operations are performed on the signals, and then the gradation toner signals of the process colors are converted into binary (on/off) toner signals, which are output to the IOT 34.
The IOT 34, which is provided with a scanner 40 and a photoreceptor belt 41, converts the image signals from the IPS into optical signals in the laser output section 40a, and forms latent images corresponding to the original document image on the photoreceptor belt 41 by means of a polygon mirror 40b, an F/.theta. lens 40c, and a reflecting mirror 40d. The photoreceptor belt 41, which is driven by a driving pulley 41a, has a cleaner 41b, a charging device 41c, and individual developers 41d for Y, M, C and K, and a transfer device 41e arranged around it. A transfer unit 42 provided in opposite this transfer device 41e takes up a copying sheet as it comes transported from the paper tray 35 via a paper transport channel 35a, and has the toners transferred in the sequence of Y, M, C and K onto the copying sheet, with a transfer belt being rotated four times, for example, in the case of full-color copying of four colors. The copying sheet with the toners thus transferred onto it is then transported from the transfer unit 42 via a vacuum transport device 43 to a fuser 45, where the copying sheet is processed for the fusing of the toners on it and is thereafter discharged. A copying sheet may selectively be fed into the paper transport channel 35a from a single sheet inserter (SSI) 35b.
The U/I 36 is operated by a user for selecting desired functions and for giving instructions as to conditions in execution of the selected functions. The U/I 36 is provided with a color display 51 and a hard control panel 52 mounted by the side of the display 51, and is further combined with an infrared touch board 53, so that instructions may be given directly by operations of soft buttons on the screen.
A film projector (F/P) 64 and a mirror unit (M/U) 65 together form a film image reading unit. FIG. 6 is a perspective view of the F/P 64; FIG. 7 is a perspective view of the M/U 65; FIG. 8 is a chart illustrating the density characteristics of a negative film and the principle of density correction; and FIG. 9 is a chart illustrating the schematic construction of the F/P 64 and the relationship among the F/P 64, M/U 65 and IIT 32.
The F/P 64 has a housing 601, as shown in FIG. 6, and this housing 601 is provided with an operation checking lamp 602, a manual lamp switch 603, an automatic focus and manual focus changeover switch (AF/MF changeover switch) 604, and manual focusing operation switches (M/F operation switches) 605a and 605b. Moreover, the housing 601 is provided with an opening/closing part 606 which can be opened or closed freely, and holes 608 and 609 having sizes large enough to accept a film holding case 607 holding original document films 633 as inserted into the housing 601 either vertically or laterally through them, depending on the manner how objects have been photographed on the films 633. On the opposite side of these holes 608 and 609, there are made other holes (not illustrated) through which the film holding case 607 can protrude.
The film holding case 607 is provided with a case for a 35 mm negative film and positive film, and the F/P 64 is constructed so as to be capable of projecting these types of films. Also, the F/P 64 is constructed so as to be capable of projecting negative films having the size of 6 cm.times.6 cm and 4 inches.times.5 inches, respectively. In the latter case, the F/P 64 holds the negative film between the M/U 65 and the platen glass 31 so that the film is kept in close contact with the platen glass 31.
As shown in FIG. 9, a reflector 612 and a light source lamp 613 such as a halogen lamp is arranged on the same axis as a projector lens 610 in the housing 601. In the proximity of the lamp 613 is installed a cooling fan 614, which cools this lamp 613. Furthermore, on the right side of the lamp 613, an aspherical lens 615 for converging the light emitted from this lamp 613, a heat ray absorbing filter 616 for cutting off part of the light in a predetermined wavelength range, and a convex lens 617 are respectively arranged on the same axis as the projector lens 610.
On the right side of the convex lens 617 is installed a correcting filter automatic exchanging device which is provided with a correcting filter holding member 618 which holds density correcting filters 635 for a 35 mm negative film and positive film (only the correcting filter for one of these types of film is shown in the figure), a driving motor 619 for this correcting filter holding member 618, first and second position detecting sensors 620 and 621 for detecting the rotational positions of the correcting filter holding member 618, and a control device for controlling the driving motor 619 (this control device is installed in the F/P 64 but not shown in the figure). The correcting filter automatic exchanging device is constructed so as to make automatic selection of a correcting filter 635 suitable for the original document film 633 out of the correcting filters 635 held on the correcting filter holding member 618, and to set the selected filter in its proper position on the same axis as the individual lenses including the projector lens 610. The correcting filters 635 in this correcting filter automatic exchanging device may be arranged in any place, such as in the space between the platen glass 31 and the imaging unit 37, for example, as long as the location is on the optical axis of the projected light.
In addition, the F/P 64 is provided with an automatic focus sensor light emitter 623 and detector 624 which work in association with the projector lens holding member 611, and a sliding motor 625 which slides the projector lens holding member 611 in relation to the housing 601. When the film holding case 607 is inserted into the inside of the housing 601 either through the hole 608 or the hole 609, the original document film 633, which is held in this film holding case 607, is positioned between the correcting filter holding member 618 and the light emitter 623 and detector 624. In the neighborhood of the position where the original document film 635 is to be set, a film cooling fan 626 is provided for cooling off this original document film 633.
As shown in FIG. 7, the mirror unit 65 is provided with a bottom plate 627 and a cover 628 with one of its ends rotatable engaged with the bottom plate 627. Between the bottom plate 627 and the cover 628 are mounted a pair of supporting pieces 629 and 629 to form a joining link for a frame structure, and these supporting pieces 629 and 629 are so constructed as to support the cover 628 in such a manner that the angle which this cover 628 forms with the bottom plate 627 will be 45 degrees when the cover 628 is opened to its maximum degree.
On the back surface of the cover 628 is provided a mirror 630. A wide opening is formed in the bottom plate 627, and a Fresnel lens 631 and a diffusing plate 632 are provided to close up this opening.
This Fresnel lens 631 and diffusing plate 632 are made of one acrylic resin plate, and the Fresnel lens 631 is formed on the upper surface of this acrylic resin plate while the diffusing plate 632 is formed on its lower surface. The Fresnel lens 631 has the function of preventing the darkening of the peripheral region of the image by transforming the projected rays, which, being reflected by the mirror 630, tend to disperse, into parallel rays. The diffusing plate 632 has the function of diffusing by a little amount the parallel rays from the fresnel lens 631 in order to make non-detectable by a line sensor 226 a shadow of a selfoc lens 224 in the imaging unit 37 which would otherwise be produced by the parallel rays.
In general, the range of the density available on films is wider than the range of density on document originals. Also, the range of density will very depending on the type of film. For example, the range of density on a positive film is wider than that on a negative film. Moreover, the range of density on a film will vary depending on the photographing conditions of an original document film, such as the amount of exposure to light, the density of an object, and the brightness at the time when a photograph is taken. As a matter of fact, the density of an object is in a wide distribution within the range of density of a film.
Therefore, in case it is intended to copy images recorded on such films by means of a copying machine which copies images on an original document using reflected light, a single type of signal processing method could not provide favorable reproduction performance. Therefore, a copying machine is designed, to achieve a favorable reproducing performance, so as to make an appropriate correction on the signals read of images in such a manner that the density of the principal objects will adequately be reproduced.
FIG. 8 illustrates the density characteristics of a certain negative film and the principle of density correction. In this figure, the right half of the horizontal axis represents the amount of exposure from an object (which corresponds to the density of an object), while the left half represents the density after subjected to the shading correction. The upper half of the vertical axis represents the output from the video circuit (the output being approximately equal to the density on the negative film), while the lower half represents the density on an output copy. That is to say, the first quadrant expresses the density characteristics of the negative film; the second quadrant shows the shading correction; the third quadrant indicates of the .gamma.-correction; and the fourth quadrant indicates the relationship between the amount of exposure of from an object and the density of the output copy as corrected.
The density characteristics of this negative film are indicated by the line alpha in the first quadrant of FIG. 8. Specifically, the more the amount of exposure from an object is, the higher the density of the negative film will be, and, as the amount of exposure from an object decreases, the density of the negative film will become smaller in linear proportion. When the amount of exposure from an object falls below a certain level, the linearity between the amount of exposure from an object and the density of the negative film will be lost. If this amount of exposure is small, it will be impossible, for example, to render a face and hair of a human bust recorded on the film in a proper contrast. Even in case the amount of exposure is large, since the inclination of the line alpha, i.e., .gamma. is smaller than one, resultant copy images will have a soft tone unless a .gamma.-correction is made. Therefore, it is understood that the .gamma.-correction is required.
Next, a description is made of the principle of corrections with reference to FIG. 8. In the third quadrant in the figure, END (Equivalent Neutral Density) curves .beta. are set for the purpose of the .gamma.-correction. The inclination .gamma.' of the END curves .beta. is set so as to maintain the relationship, .gamma.'=1/.gamma., so that the relationship between the amount of exposure from an object and the density of the output copy will be linear at the angle of 45 degrees in the fourth quadrant.
First, the region a is considered in which case the exposure amount form an object is relatively large. If the density adjusting value set in a register in the shading correction circuit corresponds to the straight line (4) in the second quadrant, the density after the shading correction will be distributed over the region a'. Since the part a" of the region a' will be out of the conversion range of the END curves .beta., this part a" will entirely be rendered white in a resultant copy. Thus, the density adjusting value is shifted from the straight line (4) to the straight line (1) in the second quadrant, so that the density after the shading correction is adjusted so as to be within the range of conversion according to the END curves .beta.. With the adjustment made in this manner, the relationship between the amount of exposure from an object and the density of the output copy will be along the straight line (1) at the angle of 45 degrees in the fourth quadrant, so that the density of a resultant copy will have a proper chromatic gradation.
In the case of the region b, where the amount of exposure from an object is relatively small, linearity in the relationship between the amount of exposure from an object and the density of the negative film will be lost. In this case, the density adjusting value in the shading correction circuit is set in the value of the straight line (4) in the second quadrant, and the END curve .beta. indicated by the line (4) in the third quadrant is selected. The selection of this line (4) can hold the amount of exposure from an object and the density of the output copy in the relationship indicated by the straight line (4) at the angle of 45 degrees in the fourth quadrant. That is to say, it becomes possible to produce a distinct contrast between dark hair of a person and a brown hat he wears even if the amount of exposure from an object is in the region b, preventing the hair and the hat from being rendered in almost the same degree of density. Thus, corrections are made in the above manner so that the density of an object is adequately reproduced.
The processing of picture image signals will be described with reference to FIG. 9. A line sensor 226 reads the projected rays of the picture images on the original document film 633 to produce analog image signals representing respective light quantities of R, G and B, and an amplifier 231 amplifies the image signals to prescribed levels. The amplified image signals are then converted into digital signals by an analog-digital (A/D) converter 235, and further a logarithmic converter 238 converts the light quantity signals into the density signal.
The image signals expressed in density are processed for the shading correction by a shading correction circuit 239. This shading correction removes from the image signals irregularity in light quantity caused by the selfoc lens 224, irregularity in sensitivity of individual pixels of the line sensor 226, variations in spectral characteristics and light quantity of the correcting filters 635 and the lamp 613, and components reflecting the effects of changes with the passage of time.
Prior to the performance of this shading correction, a correcting filter for the positive film is first set in case any of the three types of films mentioned above and the registered films has been selected as the original document film. The light quantity signals from the lamp 613 are read with the original document film 633 not yet set, amplified, and converted into digital signals, and finally converted into density signals. Data obtained on the basis of the density signals are stored as reference data in a line memory 240. Specifically, the imaging unit 37 scans 16 lines by stepped scanning to perform sampling for each of the pixels of R, G and B, and the sampling data thus obtained are transferred to a central processing unit (CPU) 634 by way of the line memory 240. The CPU 634 calculates an average density value of the sampling data for the 16 lines, thereby developing the shading data. By thus calculating the average value, errors existing in individual pixels are eliminated.
When images are read from an original document film set in its position, the CPU 634 calculates a density adjusting value D.sub.ADJ on the basis of the density data of the negative film as stored in a read only memory (ROM), and rewrites the D.sub.ADJ value already set in a register of an LSI in the shading correction circuit 239. Further, the CPU 634 adjusts the intensity of light emitted from the lamp 613 and the gain of the amplifier 643 in correspondence with the selected film.
Then, the shading correction circuit 239 shifts the density values by adding the D.sub.ADJ value to the actual data read of the original document film. Furthermore, the shading correction circuit 239 makes the shading correction by subtracting the shading data on individual pixels from the data adjusted above.
When a film is of a type not registered either in the ROM of the CPU 634 or in a random access memory (RAM) of the system, it is necessary to obtain density data of the film from a base film set for it, and to calculate the D.sub.ADJ value from the density data thus obtained.
When the shading correction is finished, the IIT 32 outputs the density signals R, G and B to the IPS 33.
Then, the CPU 634 selects an END curve on the basis of the actual data of the original document film, and outputs a correcting signal for a .gamma.-correction on the basis of the selected curve. Using the correcting signal, the IPS 33 performs the .gamma.-correction to correct the unsatisfactory contrast performance which would otherwise be caused by the .gamma. value being smaller than one and the non-linear characteristics.
However, images photographed on a film with a camera generally have subtle differences which not only result from the type of film, but also depend on various conditions such as the type of camera, the photographing conditions, such as the amount of exposure, set by the person who has taken the photograph, the composition of a picture, and the brightness of a photographed object. For example, even in respect of the photographing conditions alone, the hue on the whole will vary among such cases as a photograph taken under intense rays of the sun in a fine weather, a photograph taken with a stroboscope at night, a photograph taken of a landscape with a high ratio of verdure, a photograph taken of a person, and so forth. Particularly on a photograph taken of a person by stroboscopic photography, the person's figure, which is the principal object, will be rendered in an approximately normal density as the strobe light of a sufficient amount reaches him, but the background around the person's figure is rendered darker on the whole since the strobe light does not reach it.
In order to produce color copies in stable picture quality from images on a film, using a color copying machine, it is necessary to perform such various processes as the color balance adjustment and density adjustment in an appropriate manner on each image since there are delicate differences in such factors as brightness as described above. Therefore, in order to read a color film image and produce copies thereof, it is required to perform a prescanning operation, in advance of a main scanning operation, thereby sampling information on the film image and extracting necessary parameters. In such a case, however, extracting parameters for the image adjustments by sampling image information at various points on the film would require stepped scanning to perform the sampling of data on a plural number of lines. In addition, arithmetic operations would be needed for the collection of data at a plural number of sampling points on each line, the arithmetic operations including the judgment of hue and the determination of the amount of density adjustment at each sampling point. Consequently, the duration of time required for the processing of a single line is extended. That is to say, there arises a problem that prompt services cannot be offered because the duration of time from the start of the operation to the generation of a desired copy output will be prolonged as it is difficult to shorten the prescanning period.